With the proliferation of cellular phones, there has been pressure to improve the battery power capability to supply these devices. The efficacy of these phones relies on mobility and such mobility requires efficient battery power. From the start the batteries used have been rechargeable, prompting significant development in the structure of rechargeable batteries. Under normal conditions, the charging of such batteries is accomplished by circuitry built into the control microprocessor of the cellular phone. In order to operate, however, the controller requires a minimum voltage level from the batteries. A problem therefore arises when the battery charge is depleted below the voltage required to power the microprocessor control unit (MCU). Without the benefit of the MCU, the charger current can be applied to the battery even if damaged, partially disabled or at high temperature. This can result in damage to an otherwise useful battery or to the charging circuit.
In prior art systems, such damage is sought to be avoided by providing the low voltage start-up charging circuit with a timer. If the operational threshold of the MCU is not attained within a preset period, then the charging circuit is shut down. In addition some prior systems provide an overall voltage ceiling, which, if exceeded, will result in the shut down of the timer. Such systems to not take into consideration, the temperature of the battery at charger start-up nor the condition of battery.
It is a purpose of this invention to provide an improved charging system for depleted batteries in which modified circuitry is inserted into the energy management integrated circuit of the MCU to prevent charging when the battery is at excessive temperatures or non-functional.